In the electrical or electronics industry, there is great use of ferrite "E-cores" for use as magnets in various wound core assemblies. In order to assure proper magnetic flow, it is necessary for the faces of the E-cores to be extremely flat, and with relatively good surface smoothness, so that a constant, smooth flow is provided to the magnetic path. This requires an operation after firing of the ferrite to provide the flat, smooth surfaces. Machines for accomplishing this are sold by Speedfam Corporation of Des Plaines, Illinois, for example the Through-Feed Grinder.
Hitherto, ground E-cores have been provided with the two outer arms and the central arm being all of substantially the same length.
In some products, there is a need for the center leg of E-cores to be shorter than the two outer legs to provide an air gap between two mated coils. Difficulties exist in the production of such a design of E-core, where the middle arm is generally 0.002 to 0.04 inch shorter than the outer arms. Generally, a separate grinding step for the middle arm is required, which results in a significant increase in the cost of manufacturing E-cores of that design.
In accordance with this invention, a grinding apparatus is disclosed, modified to grind items, and specifically E-cores, in more than one plane, so that first and second ground areas on the product may be in different planes. The grinding procedure may be performed in a single operation, without need to mount the items to be ground into two different machines in two different productions. Thus, a considerable saving in manufacturing costs can be achieved, while at the same time improved accuracy of grinding can be obtained since the two planes of grinding may be well correlated with each other.
Not only is the apparatus of this invention contemplated for the grinding E-cores, but any desired workpiece may be ground in the apparatus of this invention, for single step grinding in two or more planes.